Offshore platform



Feb. 28, 1961 E. L. THEARLE 2,972,973

OFFSHORE PLATFORM Filed May 6, 1958 3 Sheets-$heet 1 300 2 9 291, 06 r8%; q BBQ INVENTOR.

I 1i ERNEST L. 771mm: i W 5% Feb. 28, 1961 E. L. THEARLE 2,972,973

OFFSHORE PLATFORM Filed May 6, 1958 r 3 Sheets-Sheet 2 INVENTOR. ERA/57L. THEARLL' BY WW- A TTOENE) Feb. 28, 1961 THEARLE 2,972,973

OFF SHORE PLATFORM Filed May 6, 1958 5 Sheets-Sheet 3 55 v 55 28a 28bINVENTOR.

EBA/57 L. THEAQLE BY V W ,4.

United grates Patent QFFSHORE PLATFORM Ernest L. Thearle, 12710 S. 3rdSt., Yucaipa, Calif.

Filed May 6, 1958, Ser. No. 733,284

3 Claims. (Cl. 114-435) 2,972,973 i s F .1.

hull 11 provided with three ballast tanks 12 which are disposedsymmetrically with reference to the vertical axis of the hull. The hullmay be cylindrical as shown, or it may be hexagonal or other suitableshape. It is a closed tank which provides the necessary buoyancy. Thebuoyancy is varied and controlled by the amount of water admitted to orexpelled from the ballast tanks 12.

The superstructure 13 is supported by slender tubular members 14 whichoffer a minimum resistance to move ment of water. The water is shown at15, its surface being shown at 15a. The superstructure 13 comprises twodecks, to wit, a lower machinery or operating deck operations, for radarstations and as heliports, include the following: The platform should berelatively unaffected by tides or wave motion and by changes in theamount or distribution of the live load. Also, it is preferably capableof being anchored in relatively deep water and of being moved withoutundue difficulty from one location to another.

Heretofore, to my knowledge, offshore platforms satisfying theseobjectives have not been provided, unless, perhaps, by the use ofextremely complex machinery and equipment.

It is an object of the present invention to provide an improved offshoreplatform of the floating or buoyant type.

It is another object of the invention to provide a stable offshoreplatform which is of the floating or buoyant type and whose working deckremains in a predetermined horizontal plane substantially unaffected bytides, wave motion and live load.

Yet another object is to provide a stable oflshore platform of thegeneral character described which can be anchored in relatively deepwater, and which can be moved without undue difficulty fro-m one site toanother.

These and other objects of the invention will be apparent from theensuing description and the appended claims.

Certain forms of the invention are illustrated by way of example in theaccompanying drawings in which:

Figure 1 is a view in side elevation of the platform of the invention.

Figure 2 is a section taken along the line 22 of Figure 1, such sectionbeing taken in a horizontal plane beneath the working deck and showingin top plane view and more or less diagrammatically, the machineryemployed to operate the platform.

Figure 3 is a view in side elevation of one of the automatic weighingand adjustment units, there being three pairs of such units, one memberof each pair being intended to adjust the ballast and the other memberbeing intended to adjust tentacle tension directly by Winch control.

Figure 4 is a diagrammatic view of a control circuit for operating apair of the weighing and adjustment units, one of which is shown inFigure 3.

Referring now to the drawings and more particularly to Figures 1 and 2,the platform is generally indicated by the reference numeral 10. Itcomprises a buoyant 16 and an upper working deck 17. It is the latterdeck (the deck 17) which is intended to support drilling equipment,radar equipment or the like or to serve as a landing platform foraircraft such as helicopters.

The platform 10- is anchored to the sea bottom 18 (or to the bottom of alake, river or other body of water), by anchors 19 and anchor cables 20.The anchor cables 20 pass under sheaves 25, thence upwardly to anchorwinches 26. Preferably the sheaves 25 are so placed that the anchorcables 20, if extended as tangents to the sheaves 25, would meet atapproximately the center of the working deck 17. The platform 10 ispreferably a three-celled structure as shown, hence there are preferablythree anchor cables 20. However, the principles of the invention areapplicable to a different number of cells, for example, four in whichcase a like number of anchors and cables will be employed. Forconvenience of reference the three cells are indicated as A, B and C.However, since the three cells are identical only one need be described.

It is the purpose of the anchors 19 and anchor cables 20 to restrain theplatform 10 from lateral movement. The more difficult function ofholding the working deck .17 in a fixed, horizontally plane isaccomplished by weights or spuds 27a, 27b, tentacles 28a, 28b and themachinery and control equipment located on the deck 16; Each of thecells A, B and C has associated with it the following equipment: A pairof spuds 27a, 27b; a pair of tentacles 28a and 23b; a pair of tentaclewinches 29a, 2%; one ballast tank 12; one anchor winch 26; two automaticweighing units 30a, 3%, one of which is shown in Figure 3; and a controlcircuit 31 (see Figure 4). It will be understood that a suitable primemover (e.g., a diesel engine) will be provided to supply power foroperating this equipment. Thus, a single diesel engine-electricgenerator combination may be provided for the entire platform 10 andeach winch may be provided with an individual electric motor powered bythe electric generator.

Referring now to Figure 3, the weighing unit 30a of cell A is thereshown. All of the other five weighing units (i.e., the unit 3011 of cellA and the units 30a and 30b of cells B and C) are identical. Therefore,detailed description of this one unit will suflice.

As will be seen, the tentacle 28a passes over a large sheave 35 whichforms a part of the weighing unit 30a. The sheave 35 is journaled at 36in a lever 37, such lever being fulcrumed at 38 on brackets 39, one ofwhich is shown in Figure 3. The free end of the lever 37 passes througha stop member 40 which is fixed to the deck 16, and which serves thepurpose of preventing extreme motion of the lever. An expansion spring45 and a screw 46 opposing the spring are provided to hold the lever 37normally in whatever position desired. The

extreme outer end of the lever 37, which is indicated by I 49 and 50 aresupported by a bracket 51 which is fixed to the deck 16. Thepressure-responsive device 49 is connected by tubing 52 to apressure-responsive switch 53. The other pressure-sensitive element 50is connected by tubing 54 to apressure-responsive switch 55'. A branchtube 60 connects the pressure sensitive element 50 to a thirdpressure-responsiveswitch 61.

- The weighing unit 30a illustrated in Figure 3 is the ballast controlunit of cell A. That is, the unit 30a is intended to control the ballastin the ballast tank 12 of cell A. This ballast tank (as well as theother two ballast tanks) is provided with an inlet valve 62 and anoutlet pump 63 (which are shown in Figure 4) to admit and dischargewater respectively.

Suppose that the tentacle 28a shown in Figure 3 is relaxed because ofinsuiiicient buoyancy. The lever 37 will rotate in counterclockwisedirection as viewed in Figure 3, thereby relieving pressure in bellows5t} and in switch 55. The switch 55, therefore, closes and starts theballast pump 63 of cell A. Pump 63 pumps water out of the tank 12 ofcell A, thereby increasing the buoyancy of cell A until it reachesitsnormal value. If, on the other hand, there is excessive tension in thetentacle 28a; the lever 37 will rotate in clockwise direction therebyrelieving pressure in bellows 49 and in switch 53, which will open theballast valve 62 of the ballast tank 12. The buoyancy of cell A is,therefore, decreased until the normal value is reached. 7

As stated above, cell A is provided with a second weighing unit 30bwhich is similar to the weighing unit 30a, but it is connected to thetentacle 28b and it serves toopera'te a motor (not shown) which operatesthe winch 29b. Thus, when the tentacle 28b of cell A relaxes, lever 3.7of the weighing unit 30b, will rotatecounterclockwise and, actingthrough the bellows 50 and switch 55, it will cause the winch 29b torotate in the proper direction to take. in the tentacle 28b until theproper tension is reestablished. Similarly if the tension of tentacle28b becomes excessive, the weighing unit 30b will operate, in a mannerwhich will be apparent, to restore the proper tension. p It will beunderstood that each of the cells B and C has a pair of tentacles 28aand 28b, a pair of winches 29a and 2%, a pair of weighing units 30a and30b, a ballast valve 62. and a ballast pump 63 which operate in likemanner to maintain the proper tension in each of the tentacles 28a and28b. The system is preferably adjusted to maintain the tentacles 28a and28b between one-quarter and three-quarters of the spud weight of eachtentacle.

Referring now to Figure 4 the control circuit 31 of cell A is thereshown. Similar control circuits are pro vided for cells B and C. Figure4 shows a simplified line diagram rather than a complete circuit but itwill suifice for the purpose of illustration. Thus the weighing unit 30aoperates its pressure switches 53 and 55 (lefthand side of the diagram).Switches 53 and 55 are connected by a circuit generally indicated as 70aand which includes a transfer switch 71a, to the ballast valve 62 andballast pump 63, respectively. A solenoid 72b maintains, the switch 71anormally closed. Similarly weighing unit 30b operates its pressureswitches 53 and 55' (right-hand side of the diagram), which areconnected by a circuit generally indicated as 70b, and which includes atransfer switch 71b to the winch 2912. One of the switches 53, 55operated by the weighing unit 3015 operates the winch 29b in onedirection (to take in the tentacle 28b) and the other switch operatesthe Winch 29b oppositely to pay out the tentacle "2815. In Figure 4, thereference numerals 29c indicate reversible motors for. operating thewinches 29a and 2911.

It will be seen that two solenoids 72a and 73a are also PI ided in thecontrol circuit 31 of cell A. The sole.- noids 72a and 730: areenergized only when the low pressure switch 61 of weighing unit 3041. Ony Cell is closficb i The switch 61, which is also shown in Figure 3,closes when, for any reason, a very low pressure is reached in thebellows 50 (see Figure 3). Thus if the tentacle 28a of cell A shouldbreak, switch 61 will close, solenoids- 72a and 73a will be energizedand transfer switches 71a and 71b will shift to the opposite contactsthere energizing circuits 74a and 75b. The energizing of circuit 74awill operate winch 2901, which will haul in the broken tentacle 28a. Theenergizing of circuit 75b will connect weighing unit 30b to the ballastvalve 62. and ballast pump 63, thereby shifting weighing unit 3% anditstentacle 28b from its normal winch control to ballast control. Leads76 connect with the control circuits of cells B and C. Hence when any ofthe tentacles 28a breaks all of the weighing units 30b are placed onballast control and all of the weighing units 3G5: are placed on winchcontrol. .The winches 2% connected to unbroken tentacles 28a do notexert sufiicient force, however, to raise their spudsydue to ballastcontrol. If a tentacle 28b breaks while on winch control, winch 2% willwind in the tentacle and the ballast control of so corrects for itsloss.

Thus a continuous ballast and winch control are maintained at all times;the deck 17 is maintained fixed in space regardless of varying loads andvarying load distribution; emergency operation is provided in case anyof the ballast controlled tentacles should break; and in case ofemergency a symmetrical application of winch control is preserved.

To remove the platform from a site, the anchor winches 26 and thewinches 29a are backed oif to slacken the anchor cables 20 and tentacles28a, respectively. The weighing units 30a will, therefore, automaticallyremove ballast from the ballast tanks 12 and will provide the necessarybuoyancy until the platform surfaces and acquires its natural level andstability with its ballast tanks empty. Meanwhile the weighing units3012 will back off their winches 2% to maintain constant tension. Theweighing units 30a and 3% are then inactivated, the spuds and anchorsare raised and the platform is towed to another site. To establish thenew site the reverse procedure is carried out.

I claim:

1. A platform structure of the character described comprising a deck, abuoyant hull supporting the deck, said hull having inlet means andoutlet means to admit and expel Water and thereby decrease and increaseits buoyancy, respectively; means for anchoring the platform to restrainthe same from transverse displacement, weights opposing the buoyancy ofthe platform, cables connected to said weights and to the platform, andcontroland sensing means actuated by tension in said cables to operatesaid inlet and outlet means to increase and decrease the buoyancy of thehull and maintain the deck in a fixed horizontal plane.

2. A platform structure of the character described comprising a deck, abuoyant hull supporting the deck. said hull comprising a plurality ofballast tanks each having inlet and outlet means for decreasing andincreasing, respectively, the buoyancy of the respective tank and meansfor anchoring the platform to restrain the same from transversedisplacement; said platform structure also comprising a tentacle, aweight and a winch for each ballast tank, said weight being adapted torest on the bottom of a body of water to oppose the buoyancy oi thehull, said winch being supported by the hull, said tentacle beingconnected at one end to its weight and at its other end to its winch;and sensing and operating means for each ballast tank actuated bytension of its cable and operating the inlet and outlet means of itsballast tank to maintain said deck in a fixed horizontal plane.

3. In a buoyant type of platform of the character described comprisingabuoyant hull and a working deck supported. by the hull, and buoyancycontrol elements having means for increasing and decreasing the buoyancyof the hull to maintain said working deck in a fixed, horizontal planenotwithstanding the ebb and flow of tides and other factors tending tolift or lower the working deck, the improvement which comprises cableseach connected at one end to said platform, a weight connected to theother end of each said cable, said weights being adapted to rest on thebottom of a body of water to oppose the buoyancy of the hull, sensingmeans for sensing the tension in each cable and control means actuatedby said sensing means to operate said means for increasing anddecreasing the buoyancy to maintain the working deck in said plane.

4. In a buoyant type of platform of the character described comprising abuoyant hull and a working deck supported by the hull, and buoyancycontrol elements in the form of ballast tanks and an inlet valve and anoutlet pump for each such tank for decreasing and increasing thebuoyancy of the hull, respectively, to maintain said working deck in afixed, horizontal plane notwithstanding the ebb and fiow of tides andother factors tending to lift or lower the working deck, the improvementwhich comprises cables each connected at one end to said platform, aweight connected to the other end of each said cable and lying on thebottom of a body of water, sensing means for sensing the tension in eachcable and control means actuated by said sensing means to operate saidvalves and pumps to maintain the working deck in said plane.

5. 'In a buoyant type of platform of the character described comprisinga buoyant hull and a working deck supported by the hull and buoyancycontrol elements for increasing and decreasing the buoyancy of the hullto maintain said working deck in a fixed, horizontal planenotwithstanding the ebb and how of tides and other factors tending tolift or lower the working deck, the improvement which comprises cableseach connected at one end to said platform, a weight connected to theother end of each said cable and lying on the bottom of a body of water,sensing means for sensing the tension in each cable, said sensing meansbeing in the form of a lever pivoted by movement of such cable andpressureresponsive means operated by said lever to operate said buoyancycontrol elements to maintain the working deck in said plane.

6. A platform of the character described comprising a superstructure, ahull and a buoyancy control system; said hull having a buoyantcompartment and a plurality of ballast compartments symmetricallyarranged in relation to the vertical axis of the platform; said buoyancycontrol system comprising an inlet valve and an outlet pump for eachballast tank, a weight and a cable for each ballast tank, one end ofeach cable being connected to its weight, automatic weighing means foreach cable adopted to sense the tension in the respective cable, saidautomatic weighing means being in operative relation to its cable tocontinuously sense its tension and control means actuated by variationsin the cable tensions, said control means operating to maintain thetension of each cable between predetermined upper and lower limits byopening the inlet valve of each ballast compartment when its cabletension exceeds the predetermined upper limit and by operating theoutlet pump of each ballast compartment when its cable tension slackeusbelow the predetermined lower limit.

7. A platform structure of the character described comprising a buoyanthull having a plurality of symmetrically arranged ballast tanks eachhaving an inlet valve and an outlet pump, and a superstructure supportedby the hull, first and second weights for each ballast tank and a first,ballast controlled cable and a second, winch controlled cable for saidfirst and second weights, re spectively; a winch for each winchcontrolled cable and a reversible motor for each such winch; a cabletension sensing means for each cable, said sensing means being inoperative relation to its cable to sense the tension thereof; andcontrol means whereby the sensing means associated with each ballastcontrolled cable controls the inlet valve and outlet pump of therespective ballast tank to maintain the respective cable tension betweenpredetermined upper and lower limits, said control means being alsooperable, whenever a ballast controlled cable breaks, to shift controlof the buoyancy of the structure to the winch cables.

8. A buoyant platform structure comprising a buoyant hull, asuperstructure and a plurality of symmetrically arranged ballast tankseach having inlet means and outlet means; a ballast operated cable meansand a winchoperated cable means for each ballast tank; each said ballastoperated cable means comprising a first cable, a weight connected to oneend thereof and adapted to lie on the bottom of a body of water, a winchconnected to the other end of said first cable, a reversible motor foroperating said winch, and cable tension sensing means operated by saidfirst cable to sense the tension thereof; control means normallyconnecting each said first cable tension sensing means to the inletmeans and outlet means of the respective ballast tank to cause inflow ofwater when the tension of the respective first cable exceeds apredetermined upper value and to cause outflow of water when suchtension falls below a predetermined lower value; each said winchoperated cable means comprising a second cable, a weight connected toone end thereof and adapted to lie on the bottom of a body of water, awinch connected to the other end of said second cable, a reversiblemotor for operating said winch, and cable tension sensing means operatedby said second cable to sense the tension thereof; said control meansnormally connecting each said second cable tension sensing means to therespective winch motor to maintain the respective second cable betweenpredetermined upper and lower tension limits; said control means beingalso operable, whenever one of said first cables breaks, to connect thecable tension sensing means of the second cables with the inlet meansand outlet means of the ballast tanks.

References Cited in the file of this patent UNITED STATES PATENTS1,334,445 Gaiiney Mar. 23, 1920 1,678,472 Johnson July 24, 19281,892,125 Armstrong Dec. 27, 1932 2,147,761 Whitcomb Feb. 21, 19392,238,974 Creed Apr. 22, 1941 2,244,830 Doe et al. June 10, 19412,248,051 Armstrong July 8, 1941 2,399,656 Armstrong May 7, 19462,723,833 Burfeind Nov. 15, 1955 2,839,021 Patterson June 17, 1958

